Sulphide pigment



Patented Mar. 26, 1940 UNITED STATES? PATENT OFFICE SULPHIDE PIQMENTKenneth s. Mowlds, Baltimore, Md, assignor to The Glidden Companporation of Ohio No Drawing. Application June .28, 1938,

- Serial No. 216,324

y, Cleveland, Ohio, a cor s Claims. (01. 134-58) This invention relatesto pigments containing used where they come into contact with copper orcopper compounds, and are discolored thereby.

For example, lithopone and zinc sulphide pigments are used in the wallpaper industry both as pigment fillers in the body of the paper and inpainting the paper'with designs. when used in wall paper it hasfrequently been noticed that the pigment darkens.

On investigation it has been found that copper salts used aspreservatives in the paste applied to the paper, bleed through to thepigment with the resulting formation of black copper sulphide. Thisoccurs even though the zinc sulphide is relatively insoluble and eventhough the copper or copper compounds present are relatively insoluble.There are sufficient ions formed in the presence of water to cause theformation of the blackcopper sulphide which darkens and stains thepigment.

According to the present invention the sulphide containing pigment istreated with a salt capable of producing anions in the presence of awater, which will react with copper ions present to produce a whitecopper salt. Preferably, the copper salt formed should be relativelyinsoluble. If the copper salt formed is relatively soluble, it will inthe continued presence of water, in turn yield copper ions which willreact with sulphide ions to produce copper sulphide, although if the..use to which the pigment is put is such that its I only contact withwater is short, the white cop.- per salt formed maybe relatively solubleand still give excellent protection against staining. Also, in case thesulphide pigment'is yellow such as cadmium sulphide the coppersaltformed may be of a similar color.

Salts which may be used for treatment of the sulphide containing pigmentmay be thiocyanates, thio-sulphates, xanthates, cyanamides, and otherswhich will yield anions in the presence of water However,

calcium, and barium salts will ordinarily be'used, 7 although theinvention is by no means limited thereto. As previously pointed out thesalt should be one which will yield the anions in the presence of waterin sufficient quantity to react with the '55 copper ions with which thepigment comes in contact. In many instances it is preferred to use awater soluble salt as the treating agent. However, in cases where thepigment frequently comes into contact with water andthe concentration of10 copper ions is relatively low, a water insoluble treating salt may bepreferred.

- The treating salts may be incorporated with the v pigment in a varietyof ways. They may be added dry and thoroughly-mixed orthey may bedissolved or dispersed in water and mixed with the pigment slurry, oradded dry to the pigment slurry. For the sake of convenience and toinsure water solubletreating salt is used, as little as possible is loston filtration.

RTe'latively small percentages are effective if even distribution overthe pigment is obtained. I prefer to' use about 1%, based on the pigmentcontent, to insure non-darkening even under very adverse conditions. Anyaddition of course gives protection; amounts as .low as 0.1% give goodresults formost purposes, although higher percentages are needed wherecopper mold inhibiter is used in the paste on wall paper containing thepigment. I-Iigherv percentages may be used, but the cost is increasedunnecessarily and pigment properties are diluted. A typical example ofmy invention comprises adding 10 pounds ofsodium thiocyanate to a thickslurry of calcined lithopone containing 1000 pounds of pigment. Theslurry is agitated to insure distribution of the salt; the pigment isthen filtered and dried; Other thiocyanates may be used in place of thesodium thiccyanate. In addition to lithopone, other sulphide pigmentssuch as zinc sulphide, cadmium sulphide pigments or pigments containingthe same may be treated. In general, any light colored pigmentcontaining sulphide may be treated-in accordance with the presentinvention to prevent their staining by copper. v r

This application isa continuation in part of application Serial No.99,146, filed September 2, 1936.

I claim: 1. A white pigment composition comprising a sulphide and acyanamide.

2. A pigment composition comprising zinc sulphide and a cyanamide.

3. A white pigment comprising a sulphide pigment and a cyanamide.

4. A light. colored pigment comprising a sulphide and a cyanamide.

5. A pigment composition comprising lithopone and a cyanamide; I

6. A pigment composition comprising a calcined lithopone pigment and acyanamide.

'7. A pigment composition comprising cadmium 12. The process whichcomprises incorporating a cyanamide with a calcined lithopone to renderthe same stain resistant to copper.

13. A light colored sulphide containing pigment composition containingfrom 0.1 to 1.0% I of a cyanamide salt.

14. A zinc sulphide pigment containing from 0.1 to 1.0% of a cyan'amidesalt.

15. In the pigmentation of paper the step comprisingthe addition of awhite pigment composition comprising a sulphide and a cyanamide.

16. In the pigmentation of paper the step comprising the addition of alight colored sulphide pigment composition comprising a sulphide pigmentand a cyanamide.

17. In the pigmentation of paper the step comprising theaddition of apigment composition comprising zinc sulphide and a cyanamide.

18. In the pigmentation of paper the step comprising adding a pigmentcomposition comprising calcined lithopone and a cyanamide.

KENNETH S. MOWLDS.

